When you become pregnant, your body goes on this roller coaster ride of hormones, which results in a range of strange and unexpected changes from head-to-toe.

To help prepare you for what lies ahead, SELF spoke with Leena Nathan, an ob/gyn at UCLA Health-Westlake Village, about some of the most common and wacky ways your body changes both during and after pregnancy.

1. When you are pregnant, you'll pee when you sneeze.

Carrying a baby puts a lot of weight on your pelvic floor muscles, which control the bladder, rectum, and vagina. All of that pressure can weaken those key muscles. The result: You pee when you sneeze. You don't, however, have to deal with stress urinary incontinence for the rest of your life. If it's bothering you, try strengthening pelvic floor muscles with Kegel exercises, in which you contract and release the same muscles you use when you stop the flow of urine.

2. And you will waddle like a duck.

Relaxin, an aptly-named hormone that's released during pregnancy, is designed to help your joints relax in preparation for childbirth. "It makes your pelvis a little wider, which makes it harder to keep your balance," notes Nathan. Plus, the extra weight you're now carrying around throws off your center of gravity, which also messes with your balance.

3. You may go up a shoe size—and stay that way.

There are several reasons why you may have trouble fitting into your favorite shoes both during and after pregnancy. For one thing, relaxin causes joints all over the body to relax and spread, including the feet, making them wider than before. In addition, carrying extra water weight during pregnancy causes feet to temporarily swell. "The weight of the pregnancy can flatten feet as well," says Nathan. For some women, their feet go back to normal post-birth, while others may find that they've permanently gone up a half to a full shoe size.

4. You won't automatically get stretch marks.

That is, unless it runs in your family. "If your mom or sister has stretch marks, chances are you'll get them," says Nathan. But some win the genetic lottery and have strong enough collagen and elastin in their skin to prevent stretch marks from ever forming. If you're not one of the lucky ones, you can reduce stretch marks with retinoic acid, such as prescription Retin-A, or laser treatments. But Nathan points out that both treatments are only recommended after giving birth (retinoic acid can cause birth defects).

5. But you will get a dark line down your stomach.

And guess what: That vertical line has always been there, but it was too faint to see until now. Rising estrogen levels during pregnancy can trigger hyperpigmentation, which darkens the line down your belly, known as the linea nigra. "In most women, it resolves within the year after having the baby, but in some it's permanent," says Nathan.

6. Random people think they can touch your belly.

If it were any other body part being grabbed by a stranger, you could call the police, but for some reason, people often see a pregnant belly as an invitation to touch—without asking permission first. They likely mean well, but it if creeps you out, let them know the minute they start reaching for your baby bump that you're not comfortable having someone you don't know touching your belly. Or if they've already made contact, try touching their belly at the same time and see how they like it.

7. You can take the placenta home from the hospital.

The latest celebrity fad—fueled by both Kim and Kourtney Kardashian—involves eating the placenta post-birth. "Some are taking the placenta home to have it dehydrated and encapsulated [put into pill form] and are taking it with the presumption that it will help with lactation," explains Nathan. "But there's no good evidence for that." In fact, the placenta's role is to filter out toxins so it's unclear if consuming it is even safe.

8. Your post-pregnancy breasts will sag—or be bigger than before. Or both.

It's normal for your breasts to get bigger by a cup size or two during pregnancy while your body prepares for breastfeeding. But carrying around that extra weight on your chest for several months can stretch out the Cooper's ligaments, which support the breast, leaving them deflated and droopy. Others may hold onto that extra breast mass they gained during pregnancy and stay a cup size larger post-breastfeeding, notes Nathan.

9. Sex after pregnancy will hurt more than it did your very first time.

Sorry, but someone had to tell you. And you're not alone: A whopping 85 percent of women reported that the first time they had sex after giving birth was downright painful, especially if they had a C-section. That's because there's a dramatic drop in estrogen levels after you give birth and while you're breastfeeding. "Lactation shuts down estrogen in your body to focus on producing breast milk and to prevent ovulation," explains Nathan. "The human body has evolved to not want to have pregnancies back-to-back." The lack of estrogen causes vaginal dryness, making sex painful, and decreases libido. The good news: Your body will eventually go back to its regular hormonal cycle, according to Nathan, and your libido will return, too.

10. Your hair will fall out in clumps post-birth.

It can be alarming when you see how many strands are clogging your shower drain, but there's a good reason behind it: During pregnancy, hair follicles go into a resting state (called telogen, if you must know) so they don't shed. "That's why you tend to have thicker, shinier hair during pregnancy," says Nathan. After pregnancy, the hair follicles resume their regular cycle of growing and shedding and play catch-up, so all of the lush hair you've been holding onto starts to fall out. "In the first six months, you'll feel like you're losing a lot of hair, but you're not," she says. "You just got so used to having thicker hair."